The very first thing you need is access to a HANA server and HANA client tools. The client tools, you can download from the developer centre, and you can also get a free developer access licence for HANA from SAP. However you will have to purchase hosting from one of the several cloud based services for a HANA instance.
As far as code is concerned, for HANA the programming is done using SQL Script. Once you have access to a server, you can write some code there. I suggest you take a self-study course on HANA on openSAP site to get acquainted with the basics of practical HANA.